Tracheal Pressure Research Articles

Changes of endotracheal tube cuff pressure and its indicators in laparoscopic resection of colorectal neoplasms: an observational prospective clinical trial

BackgroundLaparoscopic surgery is a popular alternative for resection of colorectal neoplasms. Carbon dioxide pneumoperitoneum and Trendelenburg positioning in procedure can significantly increase airway pressure, when endotracheal tube cuff pressure is not monitored. This prospective observational study aimed to evaluate indicators, changes and its correlation factors of endotracheal tube cuff pressure during laparoscopic resection of colorectal neoplasms.Methods122 patients scheduled for laparoscopic resection of colorectal neoplasms under propofol/remifentanil total intravenous anesthesia with orotracheal intubation were included. Tracheal tube cuff pressure was monitored continuously by calibrated pressure transducers. The ability of several predictors to predict out-of-range tracheal tube cuff pressure at different time points and its correlation factors were assessed.ResultsROC analysis showed that waist-to-hip ratio has the highest AUC for predicting out-of-range tracheal cuff pressure (AUC: 0.86 [95% CI: 0.77–0.95]); Tracheal tube cuff pressure provided by palpation was 41.0 (29.0−53.3) cmH20. Cuff pressure was 33.7 ± 2.9 cmH20 at 15 min and comparable at 30 and 45 min after insufflation, all values were significantly higher than 25 cmH20 (p < 0.001). Multiple linear regression showed tracheal tube cuff pressure was associated with peak airway pressure (p < 0.001).ConclusionsPatients with normal BMI undergoing laparoscopic resection of colorectal neoplasms require continuous monitoring and timely adjustments of tracheal tube cuff pressure. Compared with BMI, waist-to-hip ratio is a better predictor of out-of-range tracheal tube cuff pressure.Trial registrationChinese Clinical Trial Registry, identifier: ChiCTR2100054089, Date: 08/12/2021.

Impact of High-Flow Nasal Cannula Oxygen Therapy on the Pressure of the Airway System in Humans.

The understanding of how pharyngeal pressure is transmitted to the trachea with high-flow nasal cannula (HFNC) implementation and the behavior of tracheal pressure in the presence of mouth leaks remains limited. This study aimed to assess the impact of HFNC administration on tracheal pressure by comparing measurements taken with open and closed mouth with varying flows. A crossover study was conducted between March 2019 and June 2023. Subjects age > 18 years, with a tracheostomy and who were in the process of decannulation were included. Tracheal and pharyngeal pressures were measured by using specific devices, with different HFNC flows and mouth conditions. Nine subjects were assessed: 77% women, with an average age of 60.5 years. Tracheal pressure was significantly higher than pharyngeal pressure only in baseline conditions (P = .03). With regard to the rest of the scenarios, there were no significant differences between both pressures. Tracheal pressure was higher than the baseline condition both with an open mouth and a closed mouth (P = .02). The tracheal pressure at 60 L/min with an open mouth was higher than at 40 L/min (P = .042). The median pharyngeal pressure with a closed mouth was higher than with an open mouth, both with 40 and 60 L/min of flow (P = .048 and P < .001, respectively). Pharyngeal pressure at 60 L/min with an open mouth was higher than both baseline condition and at 40 L/min (P = .002 and P = .043, respectively). However, pharyngeal pressure with the closed mouth was significantly higher than with the open mouth both with 40 and 60 L/min of flow (P = .031 and P = .02 respectively). The implementation of HFNC changes airway pressures with values that impact at a tracheal level as the flow used increases. Our data contribute to the difficult interpretation of the existing interrelation between the programmed flow and its effects on the respiratory system.

Ultrasound guided transcutaneous phrenic nerve stimulation in critically ill patients: a new method to evaluate diaphragmatic function.

Diaphragm dysfunction is common in intensive care unit and associated with weaning failure and mortality. Diagnosis gold standard is the transdiaphragmatic or tracheal pressure induced by magnetic phrenic nerve stimulation. However, the equipment is not commonly available and requires specific technical skills. We aimed to evaluate ultrasound guided transcutaneous phrenic nerve stimulation for daily bedside assessment of diaphragm function by targeted electrical phrenic nerve stimulation. In this randomized cross-over study we compared a new method of ultrasound guided transcutaneous electrical phrenic nerve stimulation (SONOTEPS method) using a peripheral nerve stimulator, with the magnetic phrenic nerve stimulation. Intensive care unit adult patients under mechanical ventilation with a Richmond-Agitation-Sedation-Scale score of -4 or -5 were included. Each patient received the two methods of stimulation, in a randomized order. The primary outcome was the tracheal pressure (Ptrach) induced by stimulation. We analyzed 232 measures of Ptrach from 116 patients of whom 77 presented a diaphragm dysfunction (Ptrach < 11 cmH2O) and 50 a severe diaphragm dysfunction (Ptrach < 8 cmH2O). The Passing-Bablok regression showed no significant differences (intercept A of -0.03 [CI95:-0.83-0.52] and slope B of 0.98 [CI95:0.90-1.05]) between SONOTEPS method and magnetic stimulation which were positively correlated (R²=0.639). The mean bias was -1.08 (CI95 5.02, -7.18) cmH2O. The receiver operating curves showed an excellent performance for the diagnosis of diaphragm dysfunction and severe diaphragm dysfunction with respectively an area under curve of 0.90 (CI95 0.83-0.97) and 0.88 (CI95 0.82-0.95). This performance was not significantly affected by the body mass index or the presence of a neck catheter. The SONOTEPS method is a simple and accurate tool for bedside assessment of diaphragm function with ultrasound guided transcutaneous phrenic nerve stimulation in sedated patients with no or minimal spontaneous respiratory activity.

Valves for the Voiceless: Time to Speaking Valve Use in Posttracheostomy Patients After Multidisciplinary Initiative.

To review speaking valve (SV) use at a tertiary academic medical center and determine whether a multidisciplinary team implementation of SV protocols increased SV use and decreased time to SV trials. Retrospective case series of patients who underwent a tracheostomy between 2017 and 2023 before and after the dissemination of new protocols from a new multidisciplinary tracheostomy care initiative in 2019. The calendar days between meeting SV eligibility criteria and initial trial of SV were compared. Eligibility criteria for SV was defined as any patient ≥48 hours posttracheotomy who can breathe unassisted, off mechanical ventilation, tolerate a deflated cuff, and participate in an evaluation. Interrupted time series analysis using segmented negative binomial regression assessed the change in time to SV placement before and after protocol implementation. A total of 421 patients were identified. After new protocols were disseminated, eligible patients with a SV trial increased from 75% to 95% with an increase in percentage of patients who tolerated the SV on their first attempt from 60% to 75%. Interrupted time series analysis demonstrated protocol implementation was associated with an overall 80% decrease in time to SV placement. Continued barriers to SV implementation such as elevated tracheal pressures due to large tracheostomy sizes, or inappropriately early consultations with patients unable to participate in SV exam, may be amenable to further institution-level quality improvement initiatives. A multidisciplinary initiative's dissemination of protocols with algorithms for SLP consultation and SV use can help standardize post-operative tracheostomy care.

Functioning of unidirectional ventilation in flying hawkmoths evaluated by pressure and oxygen measurements and X-ray video and tomography.

Flying sphingids generate unidirectional ventilation with an inflow through the anterior thoracic spiracles and an outflow through the posterior thoracic spiracles. This phenomenon was documented by the CO2 emission and tracheal air pressure in split-chamber experiments in preceding studies. In the present study, we evaluated the function of the air pump mechanism by measuring the tracheal pressure and PO2in the air sacs and monitoring the wing beat using photocells. Microelectrodes recorded the abdomen flexing muscles and abdominal transverse muscle septum. The crucial structure was the vertical mesophragma, with longitudinal flight muscles attached anteriorly and large fused metathoracic air sacs posteriorly, continuous to the first abdominal segment. Longitudinal flight muscles and abdomen lifting muscles contracted synchronously, producing positive pressure pulses within the mesothoracic air sacs. In the scutellar air sacs, the PO2with starting full flight was elevated to 18-20 kPa, with a pressure increase of 35-50 Pa. In contrast, in the metathoracic air sacs, the O2 concentration during flight could rise to 10 kPa, then decline to 5±1 kPa. The metathoracic air sacs provided compliance for ventilation by the flight muscles. The initial rise and subsequent decrease of the PO2in these posterior metathoracic air sacs indicated the unidirectional flow path of the air used. Serial X-ray frames of flying Acherontia atropos visualised the cyclic phragma movement and volume changes in the metathoracic air sacs. The results showed that the contracting dorsolongitudinal flight muscles expanded the metathoracic air sacs, acting as a suction pump.

Educational Intervention Can Improve the Pilot Balloon Palpation Method of Tracheal Tube Cuff Pressure Monitoring: An Experimental Study

Abstract Background: Considerable morbidity is attributable to inappropriate tracheal cuff pressure. An earlier study undertaken in our hospital revealed that a normal cuff pressure of 20–30 cm H2O was achieved in only 6% of intubated patients using subjective estimation methods. Objective: To determine whether a training intervention could improve the accuracy of the subjective estimation method in our tracheal cuff monitoring. Materials and Methods: A 1-day training session was conducted in April 2022 for our anaesthesia providers. The cuffs of different sizes of endotracheal tubes were inflated to 25 cm H2O, and each staff was requested to feel the turgor of the pilot balloon. Subsequently, anaesthesia providers used pilot balloon palpation for the regulation of the tracheal cuff pressure in consecutive patients undergoing general anaesthesia with endotracheal intubation. During each intubation, a manometer was used to crosscheck the inflated cuff pressure objectively. The incidence of post-operative sore throat was also evaluated. The obtained outcomes were compared with pre-intervention data obtained from an earlier study conducted in the health facility from October 2020 to September 2021. Significant differences were considered when P &lt; 0.05. Results: The mean tracheal cuff pressure was improved post-intervention (49.2 ± 24.1 cm H2O versus 77.1 ± 31.1 cm H2O; P &lt; 0.001). A significantly higher proportion of tracheal cuffs (20%; 31/156) were inflated within the normal range compared to 6% (9/141) prior to the intervention (P = 0.003). Fewer patients developed post-operative sore throat following the educational intervention (32.8%; 41/125) versus pre-intervention (47.7%; 53/111; P = 0.019). Conclusion: The educational intervention improved the safety of tracheal cuff management, which could positively impact airway management, especially in poor resource settings without cuff manometers.

Upper Airway and Translaryngeal Resistance During Mechanical Insufflation-Exsufflation

Mechanical insufflation-exsufflation (MI-E) uses positive and negative pressures to assist weak cough and help clear airway secretions. Laryngeal visualization during MI-E has revealed that inappropriate upper airway responses can impede its efficacy. However, the dynamics of pressure transmission in the upper airways during MI-E is unclear, as are the relationships between anatomical structure, pressure and airflow. Can airflow resistance through the upper airway and the larynx feasibly be calculated during MI-E, and if so, how are the pressures transmitted to the trachea? Cross-sectional study of ten healthy adults, where MI-E was provided with and without active cough, employing pressure settings +20/-40 and ±40 cmH2O. Airflow and pressure at the level of the facemask were measured using a pneumotachograph, while pressure transducers (positioned via transnasal fiberoptic laryngoscopy) recorded pressures above the larynx and within the trachea. Upper airway resistance (Ruaw) and translaryngeal resistance (Rtl) were calculated (cmH2O/L/sec) and compared to direct observations via laryngoscopy. Positive pressures reached the trachea effectively, while negative tracheal pressures during exsufflation were approximately half of the intended settings. Insufflation pressure increased slightly when passing through the larynx. Participant effort influenced tracheal pressures and the resistances, with findings consistent with laryngoscopic observations. During MI-E, resistance appears dynamic, with Ruaw exceeding Rtl. Inappropriate laryngeal closure increased Rtl during both positive and negative pressures. Upper airway and translaryngeal resistance can feasibly be calculated during MI-E. The findings indicate different transmission dynamics for positive and negative pressures, and that resistances are influenced by participant effort. The findings support using lower insufflation pressures and higher negative pressures in clinical practice.

Feasibility of synchronized high flow nasal cannula.

A high-flow nasal cannula (cHFNC) delivers flow continuously (during inspiration and expiration). Using the diaphragm electrical activity (Edi), synchronizing HFNC could be an alternative (cycling high/low flow on inspiration/expiration, respectively). The objective of this study was to demonstrate the feasibility of synchronized HFNC (sHFNC) and compare it to cHFNC. Different levels of cHFNC and sHFNC (4, 6, 8, and 10 liters per minute [LPM], with 2 LPM on expiration for sHFNC) were compared in eight rabbits (mean weight 3.16 kg), before and after acute lung injury (pre-ALI and post-ALI). Edi, tracheal pressure (Ptr), esophageal pressure (Pes), flow, and arterial CO2 were measured. In addition to the animal study, one 3.52 kg infant received sHFNC and cHFNC using a Servo-U ventilator. In the animal study, there were more pronounced decreases in Edi, reduced Pes swings and reduced PaCO2 at comparable flows during sHFNC compared to cHFNC both pre and post-ALI (p < .05). Baseline (pre-inspiratory) Ptr was 2-7 cmH2O greater during cHFNC (p < .05) indicating more dynamic hyperinflation. In one infant, the ventilator performed as expected, delivering Edi-synchronized high/low flow. Synchronizing high flow unloaded breathing, decreased Edi, and reduced PaCO2 in an animal model and is feasible in infants.

Effect of cuff inflation with lidocaine, saline, and air on tracheal tube cuff pressure during laparoscopic resection of colorectal neoplasms: a randomized clinical trial

BackgroundTracheal tube cuff pressure will increase after pneumoperitoneum when the cuff is inflated with air, high pressure can cause tracheal mucosal damage. This prospective trial aimed to assess if inflating with normal saline or lidocaine can prevent increase of tracheal tube cuff pressure and tracheal mucosal damage in laparoscopic surgeries with general anesthesia. Whether changes of tracheal tube cuff transverse diameter (CD) can predict changes of tracheal tube cuff pressure.MethodsNinety patients scheduled for laparoscopic resection of colorectal neoplasms under general anesthesia were randomly assigned to groups air (A), saline (S) or lidocaine (L). Endotracheal tube cuff was inflated with room-temperature air in group A (n = 30), normal saline in group S (n = 30), 2% lidocaine hydrochloride injection in group L (n = 30). After intubation, tracheal tube cuff pressure was monitored by a calibrated pressure transducers, cuff pressure was adjusted to 25 cmH2O (T0.5). Tracheal tube cuff pressure at 15 min after pneumoperitoneum (T1) and 15 min after exsufflation (T2) were accessed. CD were measured by ultrasound at T0.5 and T1, the ability of ΔCD (T1-0.5) to predict cuff pressure was accessed. Tracheal mucous injury at the end of surgery were also recorded.ResultsTracheal tube cuff pressure had no significant difference among the three groups at T1 and T2. ΔCD had prediction value (AUC: 0.92 [95% CI: 0.81–1.02]; sensitivity: 0.99; specificity: 0.82) for cuff pressure. Tracheal mucous injury at the end of surgery were 0 (0, 1.0) in group A, 0 (0, 1.0) in group S, 0 (0, 0) in group L (p = 0.02, group L was lower than group A and S, p = 0.03 and p = 0.04).ConclusionsCompared to inflation with air, normal saline and 2% lidocaine cannot ameliorate the increase of tracheal tube cuff pressure during the pneumoperitoneum period under general anesthesia, but lidocaine can decrease postoperative tracheal mucosa injury. ΔCD measured by ultrasound is a predictor for changes of tracheal tube cuff pressure.Trial registrationChinese Clinical Trial Registry, identifier: ChiCTR2100054089, Date: 08/12/2021.

Impact of neonatal noninvasive resuscitation strategies on lung mechanics, tracheal pressure, and tidal volume in preterm lambs.

This study investigated the relationship between three respiratory support approaches on lung volume recruitment during the first 2 h of postnatal life in preterm lambs. We estimated changes in lung aeration, measuring respiratory resistance and reactance by oscillometry at 5 Hz. We also measured intratracheal pressure in subsets of lambs. The first main finding is that sustained inflation (SI) applied noninvasively (Mask SI; n = 7) or invasively [endotracheal tube (ETT) SI; n = 6] led to similar rapid lung volume recruitment (∼6 min). In contrast, Mask continuous positive airway pressure (CPAP) without SI (n = 6) resuscitation took longer (∼30-45 min) to reach similar lung volume recruitment. The second main finding is that, in the first 15 min of postnatal life, the Mask CPAP without SI group closed their larynx during custom ventilator-driven expiration, leading to intratracheal positive end-expiratory pressure of ∼17 cmH2O (instead of 8 cmH2O provided by the ventilator). In contrast, the Mask SI group used the larynx to limit inspiratory pressure to ∼26 cmH2O (instead of 30 cmH2O provided by the ventilator). These different responses affected tidal volume, being larger in the Mask CPAP without SI group [8.4 mL/kg; 6.7-9.3 interquartile range (IQR)] compared to the Mask SI (5.0 mL/kg; 4.4-5.2 IQR) and ETT SI groups (3.3 mL/kg; 2.6-3.7 IQR). Distinct physiological responses suggest that spontaneous respiratory activity of the larynx of preterm lambs at birth can uncouple pressure applied by the ventilator to that applied to the lung, leading to unpredictable lung pressure and tidal volume delivery independently from the ventilator settings.NEW & NOTEWORTHY We compared invasive and noninvasive resuscitation on lambs at birth, including or not sustained inflation (SI). Lung volume recruitment was faster in those receiving SI. During noninvasive resuscitation, larynx modulation reduced tracheal pressure from that applied to the mask in lambs receiving SI, while it led to increased auto-positive end-expiratory pressure and very large tidal volumes in lambs not receiving SI. Our results highlight the need for individualizing pressures and monitoring tidal volumes during resuscitation at birth.

Effect of continuous measurement and adjustment of endotracheal tube cuff pressure on postoperative sore throat in patients undergoing gynecological laparoscopic surgery: a randomized controlled trial.

Postoperative sore throat (POST) is a common complication following endotracheal tube removal, and effective preventive strategies remain elusive. This trial aimed to determine whether actively regulating intraoperative cuff pressure below the tracheal capillary perfusion pressure threshold could effectively reduce POST incidence in patients undergoing gynecological laparoscopic procedures. This single-center, randomized controlled superiority trial allocated 60 patients scheduled for elective gynecological laparoscopic procedures into two groups: one designated for cuff pressure measurement and adjustment (CPMA) group, and a control group where only cuff pressure measurement was conducted without any subsequent adjustments. The primary outcome was POST incidence at rest within 24h post-extubation. Secondary outcomes included cough, hoarseness, postoperative nausea and vomiting (PONV) incidence, and post-extubation pain severity. The incidence of sore throat at rest within 24h after extubation in the CPMA group was lower than in the control group, meeting the criteria for statistically significant superiority based on a one-sided test (3.3% vs. 26.7%, P < 0.025). No statistically significant differences were observed in cough, hoarseness, or pain scores within 24h post-extubation between the two groups. However, the CPMA group had a higher incidence of PONV compared to the control group. Additionally, the control group reported higher sore throat severity scores within 24h post-extubation. Continuous monitoring and maintenance of tracheal tube cuff pressure at 18 mmHg were superior to merely monitoring without adjustment, effectively reducing the incidence of POST during quiet within 24h after tracheal tube removal in gynecological laparoscopic surgery patients. The study was registered at www.chictr.org.cn (ChiCTR2200064792) on 18/10/2022.

Continuous Telemetric In Utero Tracheal Pressure Measurements in Fetal Lambs.

Normal in utero lung development and growth rely upon the expansion of airspaces and the controlled efflux of lung liquid into the amniotic space. Infants with congenital diaphragmatic hernia (CDH) also have lung hypoplasia due to occupation of the chest cavity by the stomach and bowel and, in the most severe cases, the liver. Balloon tracheal occlusion reduces the severity of lung hypoplasia in fetuses with CDH but increases the risk of premature birth. Understanding the optimal occlusion pressure and duration required to improve lung hypoplasia with tracheal occlusion is essential to improving in utero corrective treatments for CDH. The study reports a new method for continuous measurement of the intratracheal and amniotic pressures in an unoccluded and occluded fetal lamb surgical model of CDH. Time-pregnant Merino ewes underwent two recovery hysterotomies: the first at ~80 days of gestation to create the CDH, and the second at ~101 days of gestation to occlude the fetal trachea and implant an intratracheal and amniotic pressure measurement device. Lambs were delivered at ~142 days, and the pressure measurement device was removed and cleaned. The data were downloaded and filtered using a 6 h window. Transrespiratory pressure was calculated.

The use of oscillatory positive expiratory pressure devices for voice therapy

Over the last three years, a variety of oscillatory positive expiratory pressure (OPEP) devices have been commonly used by voice therapist and trainers (e.g. Acapella Choice, Shaker Deluxe, Shaker Medic Plus, New Shaker), even if they were not originally created for voice-treatment purposes. OPEP are intended to be used by physiotherapists to mobilize secretions from the lower airway when treating excessive sputum or secretion retention. The mechanism of oscillatory OPEP is based on a continuous and rapid shuttering of airflow, which in turn produces modulation of the oral and tracheal air pressure as patients blows into them. People diagnosed with cystic fibrosis and neurogenic diseases are usually recommended using OPEP devices [1, 2]. OPEP devices are different from expiratory/inspiratory muscle strength training devices, which have no oscillatory mechanisms inside.

Effects of Nasal Respiratory Support on Laryngeal and Esophageal Reflexes in Preterm Lambs.

Significant cardiorespiratory events can be triggered in preterm infants as part of laryngeal chemoreflexes (LCRs) and esophageal reflexes (ERs). We previously showed that nasal continuous positive airway pressure (nCPAP) blunted the cardiorespiratory inhibition induced with LCRs. Therefore, we aimed to compare the effects of nCPAP and high-flow nasal cannulas (HFNC) on the cardiorespiratory events induced during LCRs and ERs. The hypothesis is that nCPAP but not HFNC decreases the cardiorespiratory inhibition observed during LCRs and ERs. Eleven preterm lambs were instrumented to record respiration, ECG, oxygenation, and states of alertness. LCRs and ERs were induced during non-rapid eye movement sleep in a random order under these conditions: nCPAP 6 cmH2O, HFNC 7 L/min, high-flow nasal cannulas 7 L/min at a tracheal pressure of 6 cmH2O, and no respiratory support. nCPAP 6 cmH2O decreased the cardiorespiratory inhibition induced with LCRs, but not with ERs in preterm lambs. This blunting effect was less marked with HFNC 7 L/min, even when the tracheal pressure was maintained at 6 cmH2O. nCPAP might be a treatment for cardiorespiratory events related to LCRs in newborns, either in the context of laryngopharyngeal refluxes or swallowing immaturity. Our preclinical results merit to be confirmed through clinical studies. Laryngeal chemoreflexes can be responsible for significant cardiorespiratory inhibition in newborns, especially preterm. Nasal continuous positive airway pressure at 6 cmH2O significantly decreased this cardiorespiratory inhibition. High-flow nasal cannulas at 7 L/min had a lesser effect than nasal continuous positive airway pressure. Esophageal stimulation was responsible for a smaller cardiorespiratory inhibition, which was not significantly modified by nasal continuous positive airway pressure or high-flow nasal cannulas. Nasal continuous positive airway pressure should be tested for its beneficial effect on cardiorespiratory events related to laryngeal chemoreflexes in preterm newborns.

Tracheal tubes intracuff pressure difference between neutral head-neck position and lateral rotation in patients with tracheal intubation

BackgroundTracheal tubes (TT) cuffs seal the airway to facilitate positive pressure ventilation and prevent aspiration due to subglottic secretions. Changes in head-neck position can affect TT intracuff pressure. An increase or decrease in TT intracuff pressure can cause many morbidities. The purpose of this study was to determine the effect of lateral head-neck rotation on TT intracuff pressure. MethodsForty (40) patients aged 18–64 years undergoing elective surgery under general anesthesia were selected in this study. After tracheal intubation, the TT cuff was inflated with a minimal occlusive volume technique. The TT was placed on the right side of the mouth. Changes in TT intracuff pressure were assessed before and after the position change. TT intracuff pressure was measured with a cuff inflator in the neutral head position. After lateral head-neck rotation (60°), the intracuff pressure was remeasured. ResultsThe mean intracuff pressure increased from 25.5 + 1.64 to 29.4 + 1.71 cmH2O after lateral head-neck rotation (p = 0.000). There was a significant difference between neutral position and lateral head rotation (p < 0.05). The use of a minimal occlusive volume technique with a volume of 4–7 cc was able to produce TT intracuff pressure between 22 and 28 cmH2O (normal range 20–30 cmH2O). The difference in TT intracuff pressure after lateral head-neck rotation was 3.9 ± 1.31 cmHO2. ConclusionTracheal tube intracuff pressure is significantly higher after the head-neck position change from neutral to lateral rotation. Measurement of intracuff pressure after lateral head rotation is beneficial to avoid possible adverse effects of position-related pressure changes.

Diaphragm function in patients with Covid-19-related acute respiratory distress syndrome on venovenous extracorporeal membrane oxygenation

BackgroundVenovenous extracorporeal membrane oxygenation (VV ECMO) is frequently associated with deep sedation and neuromuscular blockades, that may lead to diaphragm dysfunction. However, the prevalence, risk factors, and evolution of diaphragm dysfunction in patients with VV ECMO are unknown. We hypothesized that the prevalence of diaphragm dysfunction is high and that diaphragm activity influences diaphragm function changes.MethodsPatients with acute respiratory distress syndrome (ARDS) requiring VV ECMO were included in two centers. Diaphragm function was serially assessed by measuring the tracheal pressure in response to phrenic nerve stimulation (Ptr,stim) from ECMO initiation (Day 1) until ECMO weaning. Diaphragm activity was estimated from the percentage of spontaneous breathing ventilation and by measuring the diaphragm thickening fraction (TFdi) with ultrasound.ResultsSixty-three patients were included after a median of 4 days (3–6) of invasive mechanical ventilation. Diaphragm dysfunction, defined by Ptr, stim ≤ 11 cmH2O, was present in 39 patients (62%) on Day 1 of ECMO. Diaphragm function did not change over the study period and was not influenced by the percentage of spontaneous breathing ventilation or the TFdi during the 1 week. Among the 63 patients enrolled in the study, 24 (38%) were still alive at the end of the study period (60 days).ConclusionsSixty-two percent of patients undergoing ECMO for ARDS related to SARS CoV-2 infection had a diaphragm dysfunction on Day 1 of ECMO initiation. Diaphragm function remains stable over time and was not associated with the percentage of time with spontaneous breathing.ClinicalTrials.gov Identifier NCT04613752 (date of registration February 15, 2021).

A Comparison of Proximal and Tracheal Airway Pressures During Pressure Controlled Ventilation.

Airway pressure is usually measured by sensors placed in the ventilator or on the ventilator side of the endotracheal tube (ETT), at the Y-piece. These remote measurements serve as a surrogate for the tracheal or alveolar pressure. Tracheal pressure can only be predicted correctly by using a model that incorporates the pressure at the remote location, the flow through the ETT, and the resistance of the ETT if the latter is a predictable function of Y-piece flow. However, this is not consistently appropriate, and accuracy of prediction is hampered. This in vitro study systematically examined the ventilator pressure in dependence of compliance of the respiratory system (CRS), inspiratory time, and expiratory time during pressure-controlled ventilation by using a small intratracheal pressure sensor and a mechanical lung simulator. Pressures were measured simultaneously at the ventilator outlet, at the Y-piece, and in the trachea during pressure-controlled ventilation with a peak inspiratory pressure of 20 cm H2O and a PEEP of 5 cm H2O while changing CRS (10, 30, 60, 90, and 100 mL/cm H2O) and varying inspiratory time and expiratory time. Tracheal pressures were always lower (maximum 8 cm H2O during inspiration) or higher (maximum 4 cm H2O during expiration) than the pressures measured proximal to the ETT if zero-flow conditions were not achieved at the end of the breathing cycles. Dependent on CRS and the breathing cycle, tracheal pressures deviated from those measured proximal to the ETT under non-zero-flow conditions. Intratracheal pressure and pressure curve dynamics can differ greatly from the ventilator pressure, depending on the ventilator setting and the CRS. The small pressure sensor may be used as a measurement method of tracheal pressure via integration onto an ETT.

The impact of endotracheal intubation on oxygen delivery, trachea pressure and wall deformation

This paper concerns improving endotracheal tube (ETT) insertion through advanced computational science modelling. The study aims to better understand endotracheal intubation (ETI) and reduce medical errors in intensive and critical care units since ETT insertion is unique for each patient, depending on age, gender, size, physiology, and underlying health conditions. We have employed computational fluid dynamics and biomechanics modelling to investigate the effect of ETT for three ventilation modes on (a) local oxygen delivery to the lungs, (b) air pressure and wall shear stress at the tracheal walls, and (c) oscillatory elastic deformation of the tracheal tissues and muscle. For the first time, we reveal how the ventilation mode and ETT insertion in the trachea may induce major complications, especially in long periods of ETT. We show that rotating the ETT or displacing it by 2 mm only can induce a significant rise in the tracheal pressure up to 177 cmH2O. This study, for the first time, shows the vital role of computers in biology and medicine to provide enhanced decision-making-support to clinicians and medical doctors dealing with ETI.

AIRFLOW ANALYSIS OF HUMAN RESPIRATORY SYSTEM AT DIFFERENT PHYSIOLOGICAL CONDITIONS

In this paper, an attempt has been made to analyze the effect of different physiological conditions i.e., rest, moderate and extremely active on the branch Reynolds number, pressure drop, lost work, alveolar partial O2 pressure, airway resistance and surface tension. From the analysis, it has been observed that local Reynolds number and tracheal pressure drop along with the generations of branch. The alveolar O2 pressure and surface tension decrease with the increased activity level. Work lost due to different major and minor losses in the respiratory tract increases with the increase in activity level. A similar trend was also found for the airway resistance i.e., increases with the increase in activity level. A new parameter, Breathing Work Number (BWN) in respiratory mechanics is introduced. BWN is the ratio of the work of breathing to the sum of work of breathing and work loss, which might find a significant application to denote the respiratory health. From the analysis, it is found that BWN decreases with the increase in activity level.

Compliance verification method on CCAR 25.1443(c) for civil aircraft passenger oxygen system based on blood oxygen saturation

This paper generally introduces the compliance verification method on airworthiness regulation CCAR 25.1443(c) of popular passenger oxygen system on civil aircraft firstly, then technical interpretation on regulation CCAR 25.1443(c) <Minimum Mass Flow of Supplemental Oxygen> is demonstrated and method of satisfying this regulation in Top-Down design is analyzed. For those passenger oxygen system based on blood oxygen saturation which is not directly fulfill the requirement of the regulation, equivalent altitude theory is established to transform mean tracheal oxygen partial pressure required by the regulation to blood oxygen saturation index of equivalent altitude, and user’s blood oxygen saturation of these passenger oxygen system is equivalent or higher than that transformed from the regulation through actual human body physiological test and theoretical analysis from aviation physiology, then compliance to the airworthiness regulation is demonstrated by Equivalent Level of Safety. This paper gives the compliance verification method on the airworthiness regulation for those passenger oxygen system based on blood oxygen saturation on civil aircraft and this method have been used and gotten approval of the Authority for a type of civil aircraft. This paper also provides theoretical basis and test basis for further airworthiness regulation revising of the regulation CCAR25.1443(c).